This invention relates to a catalyst for the dehydrogenation of cyclohexane and alkyl-substituted cyclohexanes and to a method for the dehydrogenation of cyclohexane and alkyl-substituted cyclohexanes. For brevity of description, cyclohexane and alkyl-substituted cyclohexanes will be collectively referred to hereinafter as "cyclohexanes."
It has heretofore been known in the art to produce benzene, cyclohexene, toluene, xylene, etc. by dehydrogenating cyclohexanes. This dehydrogenation is an andothermic reaciton. Thus, the large volume of heat discharged from a special chemical or other plant is utilized as a source of heat to be absorbed in the dehydrogenation which converts cyclohexanes into benzene, cyclohexene, toluene, xylene, etc. and hydrogen. In other words, this reaction of dehydrogenation can be effectively utilized for the purpose of capturing heat which would otherwise go to waste as chemical energy capable of being stored and even transported.
In this respect, the dehydrogenation of cyclohexanes has considerable industrial significance. It has been usual practice, for the gaseous-phase dehydrogenation of cyclohexanes, to use aluminum-platinum catalyst (How to Make a More Effective Platinum-Alumina Catalyst, Russell W. Maatman, Industrial and Engineering Chemistry 51 (No. 8), 913-914, 1959; Use of Platinum Group Catalysts in Petroleum and Petrochemical Industries, Tatsuo Yamanaka, Journal of the Japan Petroleum Institute 12 951-955, 1969), chromium-alumina catalyst (The Effects of Potassium on Chromia Catalyst, Sterling E. Volty and Sol W. Weller, J. Phys. Chem. 59 569-571, 1955), molybdenum-alumina catalyst (Heat Stability of Molybdena-Alumina Dehydrocyclization Catalysts, Allen S. Russell and John J. Stokes, Jr., Industrial and Engineering Chemistry 40 520-524 1948) and molybdenum oxide and chromium oxide catalyst (Oxides of the Transition Metals as Catalysts, Alfred Clark, Industrial and Engineering Chemistry 45 1476-1480 1953) which invariably use alumina as a carrier.
It should be noted, however, that alumina has a relatively low thermal conductivity (T/K) of 26.4 at 400.degree. C. and catalysts which use alumina as their carriers consequently possess poor thermal conductivity. Moreover, when the temperatuure of the reaction is elevated above 500.degree. C., a decomposition reaction occurs and the selectivity of the dehydrogenation products such as, for example, benzene and toluene, xylene is severely degraded.
The inventors continued a study in search of a catalyst which is excellent in thermal conductivity and selectivity to dehydrogenation products and, therefore, ideal for use in the dehydrogenation of cyclohexanes. They have consequently accomplished the present invention.
An object of the present invention is to provide a catalyst capable of promoting the dehydrogenation of cyclohexanes and consequently aiding in affording dehydrogenation products in high yields and with high selectivity.
Another object of this invention is to provide a method for the dehydrogenation of cyclohexanes by use of the aforementioned catalyst of the present invention, whereby the dehydrogenation products are obtained in high yields and with high selectivity.